Internal combustion engine with ducted jet fuel injection system

Abstract

Internal combustion engine (110), powered by ducted jet direct fuel injection, having a cylinder head (130) and at least one piston (140) to form a combustion chamber (150), in which the cylinder head (130) is provided with: - a channel (20) inside which an injector (170) is positioned in line with the channel (20), - a plurality of ducts (30) that branch off from the channel (20) and connect the channel (20) to the combustion chamber (150), - a plurality of features designed to promote airflow within the ducts (30). Methodology for identifying any maximum acceptable misalignments between fuel jets and ducts (30).

Description

[0001] INTERNAL COMBUSTION ENGINE WITH DUCTED JET FUEL

[0002] INJECTION SYSTEM

[0003] DESCRIPTION

[0004] Technical Sector of the Invention

[0005] The present invention relates to an internal combustion engine with ducted jet direct fuel injection.

[0006] Background art

[0007] Motor vehicles typically operate using an internal combustion engine to convert the energy of a fuel, such as gasoline or gas oil, into mechanical energy to power the vehicle's engine and consequently provide motion to the vehicle's wheels. Unfortunately, fossil fuels are costly and contribute to environmental pollution. Because of these drawbacks, attention is paid to problems of reducing fuel consumption and pollutants emitted by internal combustion engines.

[0008] To reduce harmful emissions from compression ignition engines, in particular in Diesel engines, a solution has recently been developed to improve the preparation of the mixture upstream of the premixed autoignition zone. Specifically, this is a solution that involves a ducted fuel injection, so-called Ducted Fuel Injection (DFI): DFI is based on the idea of injecting the atomized fuel through a small cylindrical tube inside the combustion chamber at a certain distance from the nozzle holes of the injector. In practice, DFI aims to increase the mixing between air and fuel before ignition (with consequent increase in combustion efficiency) and thus reduce the formation of particulate matter in Diesel engines. Recent studies have shown the high potential of this innovation for mitigating emissions in internal combustion engines.

[0009] In addition to reducing particulate emissions, through appropriate dilution of the mixture, this technology is effective in achieving a good compromise between smoke and NOx (nitrogen oxides) as well as between emissions and efficiency; it is compatible with both current conventional diesel and with oxygenated sustainable fuels; it works well over a wide range of loads.

[0010] However, the geometric and motor parameters that allow to obtain the reduction of emissions have not yet been fully understood. Furthermore, the implementation of current DFI systems presents constructive difficulties such as the exposure of the DFI to the live combustion flame, the fixing of the DFI to the cylinder head, the integration with valve and piston and the reduction of efficiency due to the high thermal exchange.

[0011] There is therefore the need to define an innovative combustion system for an internal combustion engine suitable for ducted fuel injection that minimizes the drawbacks mentioned above.

[0012] Summary of the Invention

[0013] The present invention proposes a way to solve the technical problems previously highlighted and therefore one purpose of the present invention is to define an internal combustion engine with ducted jet direct fuel injection.

[0014] According to a first aspect, the ducted jet fuel injection system is integrated directly into the cylinder head of an engine, for example a Diesel engine, suitable for medium-heavy engine applications, to improve air-fuel mixing during the injection phases and to allow very low emissions (ultralow emission).

[0015] The ducted jet fuel injection system integrated into the cylinder head allows an efficient retrofit, through standard cylinder head machining of existing Diesel engines.

[0016] According to a further aspect, a methodology is also described for evaluating and optimizing the misalignment between the holes in which the ducted fuel injectors are inserted, the fuel jets, and the axis of the latter. This methodology provides for the evaluation of both geometric and combustion parameters.

[0017] Therefore, according to the present invention, an internal combustion engine with ducted jet direct fuel injection is described, having the characteristics set forth in the independent claim of product, attached to the present description.

[0018] The present invention also provides a method for evaluating the misalignment between the duct and the fuel jet having the characteristics set forth in the independent method claim, attached to the present description.

[0019] Further embodiments of the invention, preferred and / or particularly advantageous, are described according to the characteristics set forth in the attached dependent claims.

[0020] Brief Description of the Drawings

[0021] The invention will now be described with reference to the attached drawings, which illustrate some non-limiting implementation examples, in which:

[0022] - Figure 1 is a cross-sectional view of a cylinder head (in the area of interest, with parts removed for clarity) and of the relative piston of an internal combustion engine according to an embodiment of the present invention,

[0023] - Figure 2 is a cross-sectional view, on an enlarged scale, of the cylinder head of Figure 1,

[0024] - Figure 3 is a cross-sectional view on an enlarged scale, of the cylinder head of Figure 1, in a second embodiment of the invention,

[0025] - Figure 4 is a view of the flame deck of the cylinder head of Figure 1, in a third embodiment of the invention,

[0026] - Figure 5 schematically represents the angular misalignment of the fuel spray, and

[0027] - Figure 6 is a graphical representation of the equation of the angular misalignment of the fuel spray.

[0028] Detailed Description

[0029] By way of purely exemplary and non-limiting title, the present invention will now be described with reference to the aforementioned figures.

[0030] An internal combustion engine 110, as illustrated schematically in Figure 1 (in this figure, many known components have been omitted to simplify the figure itself, which illustrates a detail of the ducted injection system integrated into the cylinder head) includes an engine block with at least one cylinder, having a piston 140 coupled to rotate a crankshaft. The cylinder head 130 cooperates with the piston 140 to define a combustion chamber 150. A mixture of fuel and air is arranged in the combustion chamber and is ignited, determining the combustion and expansion of exhaust gases that causes the alternative motion of the piston. The fuel is supplied by at least one fuel injector 170 and the air through at least one intake port. Each of the cylinders has at least two valves, operated by a camshaft that rotates in sync with the crankshaft. The valves selectively allow the entry of air into the combustion chamber from the intake port and alternatively to the exhaust gases to exit through an exhaust port.

[0031] The air can be distributed to the intake port / s through an intake manifold. An intake duct of air can supply air from the environment to the intake manifold. In other embodiments, a throttle body can be provided to regulate the air flow in the manifold. In still other embodiments, a forced air system such as a turbocharger can be provided, having a compressor coupled in a rotational manner to a turbine. The rotation of the compressor increases the pressure and temperature of the air in the manifold. An intercooler, arranged in the intake duct, can reduce the temperature of the air. The turbine rotates receiving the exhaust gases from an exhaust manifold that directs the exhaust gases from the exhaust ports and through a series of blades before expansion through the turbine. The exhaust gases exit from the turbine and are directed into an exhaust system.

[0032] The exhaust system may include an exhaust pipe having one or more exhaust gas after-treatment devices. The after-treatment devices can be any device configured to modify the composition of the exhaust gas. Some examples of after-treatment devices include, but are not limited to, oxidizing catalytic converters. Other after-treatment devices include selective catalytic reduction (SCR) exhaust gas systems. Other embodiments may include an exhaust gas recirculation system (EGR) coupled between the exhaust manifold and the intake manifold. The EGR system may include an EGR cooler to reduce the temperature of the exhaust gas in the EGR system. An EGR valve regulates a flow of exhaust gas in the EGR system.

[0033] According to the invention, the internal combustion engine 110, preferably but not exclusively a Diesel engine for medium-heavy duty applications, has a ducted injection / combustion system, inserted and integrated into the cylinder head 130.

[0034] With reference also to Figure 2, the integrated injection system in the cylinder head 130 includes an injector 170 housed in a seat 20, in the form of a channel. The seat 20 is in line with the injector 170 itself, with the piston 140 and with the combustion chamber 150. From the channel 20 depart a plurality of ducts 30 that reach the combustion chamber. Advantageously, the number of ducts 30 corresponds to the number of jets 160 of fuel coming from the injector 170 and each duct 30 is provided with an inclination with respect to the axis of the injector 170 substantially equal to the inclination of the respective fuel jet 160.

[0035] By means of this injection system, it is desired to improve the air / fuel mixture during the injection phases, increasing the air / fuel ratio.

[0036] In practice, the fuel jet 160 entrains in its motion through the duct 30 the air around it and the canalization inside the duct favoring the mixing between air and fuel. The phenomenon of mixing reduces the process of particulate formation compared to a conventional configuration (free fuel jet).

[0037] The ducted injection system according to the invention can be integrated in standard cylinder heads for Diesel engines by suitably adjusting the distance between the outlet area of the fuel jet from the injector 170 and the combustion chamber 150.

[0038] Therefore, the ducts 30 are integrated in the cylinder head 130 and are not exposed to the live combustion flame. In this way, their temperature remains under control and the heat dissipation is moderate.

[0039] It is also appropriate to give design rules for the dimensioning of the entire injection and combustion system according to the present invention. With reference also to Figure 2, conveniently:

[0040] - the protrusion between the flame plate and the center of the jet cones (SAP, Spray Apex Protrusion) must be between -3.5 mm and -9.5 mm. The SAP values are negative as in the present invention the nozzle of the injector 170 must not protrude beyond the flame plate. The selected interval of the SAP distance allows the duct 30 to be well integrated in the head 130 and also have a good extension of the hole inside the cylinder head,

[0041] - the ratio between the internal diameter D of the ducts 30 and the bore of the engine may be between 0.01 and 0.05. The selected range of this ratio allows to have a useful passage surface such as to favor the entry of the fuel and also allows to have a good interaction between jet and internal wall of the duct 30 favoring the 'Venturi' effect of the air entering the duct 30, - the ratio between the length L of the ducts 30 and the bore of the internal combustion engine may vary between 0.01 - 0.10. The length L of the duct 30 represents a fundamental parameter in relation to the mixing between fuel and air. The defined range allows a good propagation and a good mixing of the air and fuel flow. The larger the bore diameter, the larger will be the length L of the duct 30. Furthermore, the length L of the duct 30 is also a function of the SAP distance, the SA angle (spray angle) and the jets 160,

[0042] - the number of ducts 30 may vary between 4 and 12 depending on the bore of the internal combustion engine. The choice of the number of injector holes and therefore of the number of ducts 30 depends very much on the bore of the internal combustion engine, the injector 170, the space available in the head 130, the engine application and therefore on the relative level of performance and on the emission target to be achieved,

[0043] - the SA angle of the jets 160 may vary between 110° and 160° depending on the SAP distance. The SA angle of the jets 160 in a ducted jet configuration depends on the protrusion of the "tip" of the injector 170 and also on the spray targeting objective between the jet 160 and the combustion chamber 150. Furthermore, as the SAP distance of the injector decreases, for example from -3.5 mm to -7.5 mm, the SA angle of the jet 160 in a ducted jet configuration must close to avoid interaction between the ducts 30 and the valve seats.

[0044] In order to maintain a constant jet direction, a theoretical correlation between the SAP distance (mm), the SA angle (in degrees) of the jets 160 in DFI configuration, and the SA angle (in degrees) in free spray configuration is given by the following relation:

[0045] SADFI = 4.7 [° / mm] * SAP + SAFS

[0046] Furthermore, the ducted injection system is provided with further technical features to increase the air flow rate passing through the ducts 30. These features are highlighted in Figure 2, which shows a plenum at the inlet of the DFI ducts, in Figure 3, which shows a variant without the plenum and with the addition of a chamfer at the inlet of each duct, and in Figure 4, which shows the shape of the outlet of the ducts, the chamfer, and the notches in the shape of a "starfish". In particular,

[0047] - a circular connection or plenum 32 connects all the ducts 30 circumferentially in the inlet section 35 with respect to the channel 20,

[0048] - the ducts 30 have a chamfer 31 at the inlet with respect to the channel 20 of the injector 170,

[0049] - the hole of the injector seat 20 has at the outlet towards the combustion chamber 150 a predetermined chamfer 21,

[0050] - the presence of notches 37 in the area of the flame plate in correspondence of the injector seat 20 define in the cylinder head 130 a "starfish" configuration 138. This configuration favors the entry of air inside the duct 30 with relative improvements on the effectiveness of the ducted jet injection operation against the reduction of smoke,

[0051] - the ducts 30 in the proximity of the outlet section 36 towards the combustion chamber 150, have a spherical notch 33 to promote a microvorticity of the air and fuel at the outlet of the ducts 30.

[0052] Preferably, the ducts 30 are made by electro-erosion, a technique that allows to realize also the chamfers. According to the invention, the injector 170 housed in the seat 20 is the main fuel injector.

[0053] Alternatively, the injector 170 housed in the channel 20 is a further injector specifically used for ducted injection.

[0054] Conveniently the combustion chamber 150 is a combustion chamber of the "open" type. This configuration, more than the one configured "cupshaped", makes the ducted jet injection technology more effective. In particular, from experimental evidence, the combination between ducted jet injection and "open" type combustion chamber allows smoke reduction up to 40%.

[0055] The ducted jet injection system, according to the present invention, is applicable to various types of fuels, engine bore, cylinder head arrangement, rotation speed and engine load: the design characteristics can be customized accordingly while maintaining the common elements with the original design of a Diesel engine cylinder head.

[0056] The ducted jet injection system, according to the present invention, is ideal for fuels with spontaneous ignition, for example Diesel fuel, but can conveniently be used also with fuels with controlled ignition, for example ammonia or methanol.

[0057] According to another aspect, the present invention provides a method for detecting the misalignment between fuel jets 160 and ducts 30, by means of engine parameters such as combustion indices, smoke and fuel consumption.

[0058] The methodology can conveniently be used to detect the misalignment between duct 30 and fuel jet 160 during production or maintenance control.

[0059] Figure 5 shows the possible angular misalignment a of the jet with respect to the axis of the duct. In this figure, the angle P represents the opening of the jet. Furthermore, the characteristic sizes of the duct are reported in terms of length L, internal diameter d and distance G between the injector hole and the duct inlet. Furthermore, a duct 30 is illustrated, which has an axis X of symmetry, a first jet 161 of fuel angularly aligned with the axis X of the duct 30 and a second jet 162 of fuel, angularly misaligned with the X axis of the duct 30. The following parameters can be defined:

[0060] - a: maximum angular misalignment of the second jet 162 of fuel with respect to the X axis of the corresponding duct 30. Evidently for the first jet 161, the angular misalignment is equal to 0,

[0061] - P: cone angle of the jets 161 and 162 of fuel,

[0062] - d: internal diameter of the duct 30,

[0063] - G: free distance of the jets 161, 162 or distance between the exit point of the jet from the injector 170 and the inlet edge of the duct 30. This is the distance that the jet travels before being ducted.

[0064] Using these geometric parameters and some engine indices, the method allows a correlation of the engine indices with respect to the desired angular misalignment under partial load conditions and average values of NOx. The engine parameters to be taken into consideration are:

[0065] - the increase in specific fuel consumption, or

[0066] - the increase in smoke, or

[0067] - the increase in combustion duration with respect to the target values obtained with angular misalignment equal to 0 (reference values). For example, specific fuel consumption greater than 4% or doubled smoke or doubled combustion duration.

[0068] If at least one of these hypotheses is verified, then the angular misalignment of the fuel jet is greater than or equal to, respect to the maximum angular misalignment a, with: a = arcsin((d / 2) I G) - / 2

[0069] From geometric considerations, this methodology allows us to draw some conclusions:

[0070] - assuming 0=15°, the correspondence between G, d and a lower than what is reported in the following graph, the effects on the variation of fuel consumption, smoke and combustion duration are negligible and therefore acceptable,

[0071] - unburnt hydrocarbons and carbon monoxide are influenced by angular misalignment between duct 30 and jet 162 too.

[0072] In conclusion, the present invention has numerous advantages:

[0073] - the ducted jet injection system proposed is very flexible in terms of production as it can be adapted to all engine sizes and available space. Furthermore, it allows the retrofit on existing engines, sometimes making possible to reuse cylinder heads and injectors used on the original engine;

[0074] - the design of the ducted jet injection system and the methodology proposed for detecting the misalignment between duct and jet confer further robustness on the effectiveness of the ducted jet injection system in terms of reducing harmful emissions;

[0075] - the combination of the integrated ducted jet injection system to a combustion chamber of the "open" type makes it even more effective in reducing emissions;

[0076] - the ducted jet injection system can be used with different types of fuel and is therefore suitable in a fuel-agnostic perspective of the internal combustion engine.

[0077] Beyond the embodiment of the invention, as described above, it should be understood that numerous other variations exist. It should be emphasized that such embodiments are only exemplary and do not limit either the scope of the invention, nor its applications, nor its possible configurations. On the contrary, although the description above allows a person skilled in the art to implement the present invention at least according to an exemplary embodiment thereof, many variations of the described components are possible, without thereby departing from the scope of the invention, as defined in the appended claims, which are interpreted literally and / or according to their legal equivalents.

Claims

C LA I M S1. Internal combustion engine (110) powered by ducted jet direct fuel injection system, the internal combustion engine (110) comprising a cylinder head (130) and at least one piston (140) to form a combustion chamber (150), the internal combustion engine (110) being characterized in that the cylinder head (130) in turn includes:- a channel (20) inside which an injector (170) is positioned in axis with the channel (20), and- a plurality of ducts (30) which branch off from the channel (20) and connect the channel (20) to the combustion chamber (150), and by the fact that the direct injection system with ducted jet is integrated into the cylinder head and is configured to allow a retrofit by machining a standard cylinder head of existing diesel engines.

2. Internal combustion engine (110), according to claim 1, wherein the number of ducts (30) corresponds to the number of jets (160) of fuel coming from the injector (170) and each duct (30) is provided with an inclination with respect to the axis of the injector (170) equal to the inclination of the respective jet (160) of fuel.

3. Internal combustion engine (110), according to claim 1 or 2, in which the ducts (30) have an inlet chamfer (31) with respect to the channel (20).

4. Internal combustion engine (110), according to any of the previous claims, in which a plenum (32) circumferentially connects all the inlets of the ducts (35) with respect to the channel (20).

5. Internal combustion engine (110), according to any of the previous claims, in which the channel (20) has a predetermined chamfer (21) at the outlet towards the combustion chamber (150).

6. Internal combustion engine (110), according to claim 5, has notches (37) in correspondence with the flame plate and the channel (20), defining a starfish (138) configuration in the cylinder head (130).

7. Internal combustion engine (110), according to claim 6, in which the ducts (30), near the outlet section (36) towards the combustion chamber (150), have a spherical notch (33).

8. Internal combustion engine (110), according to any of the previous claims, wherein the combustion chamber (150) is an "open" type combustion chamber.

9. Method for detecting an angular misalignment between fuel jets (160) and ducts (30) in an internal combustion engine (110) according to any one of the previous claims, the method comprising the following phases: a) define the geometric parameters:- a: maximum angular misalignment of the second fuel jet (162) with respect to the axis (X) of the corresponding duct (30),- : angle of the cone of the fuel jet (162),- d: internal diameter of the duct (30),- G: distance between the apex (160') of the jet (162) and the entrance edge of the duct (35); b) evaluate the trend of at least one engine index:- increase in specific fuel consumption, or- increase in smoke, or- increase in combustion duration compared to the target values obtained with angular misalignment equal to 0; c) if at least one of these trends is verified, then the angular misalignment of the fuel jet is greater than or equal to the maximum angular misalignment (a), with: a = arcsin((d / 2) / G) - 0 / 2.

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